A US domestic flight operated by a regional partner of American Airlines has been delayed for two hours because a passenger observed a mathematics professor writing an equation in a notebook.

The woman sitting next to the professor on the plane before take-off grew fearful that he might be a terrorist writing some kind of dangerous code or formulating a plot.

Equation

The Air Wisconsin flight from Philadelphia to Syracuse ended up delayed while security intervened and asked the 40-year-old professor from the University of Pennsylvania to explain what he was doing.

Suspicions were fuelled by the fact the professor, Guido Menzio, has “dark, curly hair, olive skin and an exotic foreign accent,” the Washington Post reported.

Menzio, who is Italian, says the incident shows that anyone can delay a flight for hours, no matter how unreasonable or ridiculous their suspicion. The system is broken, he says.

According to Slate.com, the woman said initially she was feeling sick, but then confided to cabin crew she didn’t feel comfortable flying because of the man sitting next to her. Even after security personnel found there was no threat, the woman refused to reboard the flight.